When the power gets knocked out, you might think you're out of luck if you need to make a call on your cell phone. However, Make shows off how to pull power from a phone line to charge your cell phone long enough to make a call.

Obviously this is only useful if you don't have a land line, but it can certainly come in handy in a pinch. Your phone line sends a little bit of power through it, and even in blackouts it continues to work. Even if you don't have phone service, you'll sometimes (but not always) have a little bit of a charge coming through. So, using a voltage regulator, a phone cable, and a USB charger, Make creates a simple convertor that should work to power your cell phone from your phone line.